Thermal pulse ignition system



Aug. 31, 1965 A. w. VANCE 3,204,149

THERMAL PULSE IGNITION SYSTEM Filed May 24, 1962 52 54 40% :U 5o r56 36 30 l 3 ll f 2s 4s 58 3s 20 Q E E &

so 5 e4 M: J? J0 1 [3Z1 Arthur W. Vance, A i w I INVENTOR.

4 E 68 B) 76 7| "/4 78 z Z A T TORNEY.

United States Patent Office 3,204,149 Patented Aug. 31 1965 3,204,149 THERMAL PULSE IGNITION SYSTEM Arthur W. Vance, Palos Verdes Estates, Calif. (424 Mendoza Terrace, Corona Del Mar, Calif.) Filed May 24, 1962, Ser. No. 197,439 12 Claims. (Cl. 31783) This invention relates to ignition systems and more particularly to ignition systems in which the air-fuel mixture is ignited by thermal contact.

Ignition systems, particularly those used in connection with internal combustion engines, commonly employ an electrical spark to ignite the air-fuel mixture. Since elec* trical sparks may only be produced by high electrical voltages, and since high electrical voltages present difficulties when used in the normally available environments, it is a considerable advantage to employ relatively low voltage electrical signals at relatively high electrical currents to actuate the ignition system. The use of these low voltage-high current electrical signals eliminates all problems of current leakage both in the wires associated with the system and in the spark plugs. The use of an electrical spark to provide fuel ignition also produces attendant electrical noise at radio frequencies. Such noise is often very diiiicult to shield or otherwise isolate from sensitive electrical or electronic components which must necessarily be placed in close proximity to the internal combustion engine.

Briefly described, the present invention provides an ignition system utilizing an ignition element which is rapidly heated to a sufficiently high temperature such that the air-fuel mixture is ignited by thermal contact between the element and surrounding air-fuel mixture. The element is quickly heated by a relatively high electrical current pulse and is cooled by heat conduction and by the incoming air-fuel mixture. The novel ignition system provides heating and cooling of the element in such a short time that the next subsequent heating pulse may determine the time of next firing within the very short times required in modern internal combustion engines.

Since a typical internal combustion engine employs more than one cylinder, at multi-cylinder engine requires a separate arrangement or circuit to provide the necessary low voltage-high current electrical pulses to each cylinder. An appropriate timing arrangement must ensure that the electrical pulse is supplied to a particular cylinder at the proper time. In the alternative, some form of distributor arrangement must be provided. Since the use of the present invention requires the distribution of relatively high currents at low voltages rather than the typically used high voltages at low currents, a novel distributor arrangement has been devised. This novel distributor comprises a rotating type variable reluctance transformer with secondary winnings which are successively coupled to a primary winning. The necessity for any electrical contacts is eliminated and, as will be described, the device incorporates the function of an auto-transformer or transformer as well as distributing the electrical pulses to the proper cylinder at the proper time.

It is therefore an object of this invention to provide a novel and improved ignition system for internal combustion engines in which ignition of the fuel-air mixture is accomplished by an extremely rapid thermal pulse.

It is another object of this invention to provide an ignition system which uses for its actuation, electrical pulses of relatively low voltage and relatively high currents.

It is still another object of this invention to provide an ignition system which eliminates electrical current leakage in the electrical conductors used within the system and in the ignition elements.

A further object of this invention is to provide an ignition system which does not generate radio noise.

A still further object of this invention is to provide a rotating transformer or distributor device suitable for use at relatively low electrical voltages and relatively high electrical currents.

An additional and further object of this invention is to provide a distributor device which does not require any electrical contacts and which operates on a variable reluctance principle.

Further and additional objects and advantages will become apparent hereinafter during the detailed description of an embodiment of the invention which is to follow and which is illustrated in the accompanying drawings, wherein:

FIG. 1 is a view in elevation showing a conventional spark plug which has been adapted to provide for the operation of the thermal element forming a portion of the present invention.

FIG. 2 is a block diagram of the ignition system forming the present invention.

FIG. 3 is a circuit diagram showing the electrical and electronic details of a portion of the block diagram of FIG. 2.

FIG. 4 is a view in cross-section of the magnetic distributor or rotating transformer forming a part of the present invention.

Turning now to FIG. 1, there is shown a conventional spark plug which has been adapted to provide proper operation of a thermal element 10. The thermal element 10 is electrically and mechanically connected between an electrode 12 and a threaded cylindrical portion 14 which inserts into an appropriately threaded portion of a cylinder such that the thermal element 10 is in contact with the fuel-air mixture. The threaded cylindrical portion 14 establishes electrical continuity between one side of the thermal element 10 and the cylinder wall, which is normally at ground potential. The electrode 12 establishes electrical continuity between the opposite side of the thermal element 10 and also serves as an input electrode to which is supplied the electrical pulse which will be used to actuate the thermal element 10. The electrode 12 is electrically isolated from the threaded cylindrical portion 14 and from all other portions of the spark plug.

It may be seen that the thermal element 10' comprises a small relatively short rod, plate or bar of an electrically and thermally conducting material placed where the air gap is normally found in a conventional spark plug. The thermal element 10 is composed of a material which must have the ability to withstand the high temperature oxidizing and otherwise chemically active environment found in the firing chamber of an internal combustion engine and which must have a relatively high thermal conductivity so that the thermal element will be able to be cooled rapidly. In addition, the thermal element 10 must have a relatively low volume thermal capacity so that extremely rapid heating may be attained with reasonable power input.

The-material of which the thermal element 10 is composed must have a relatively low electrical resistivity so that the voltage drop developed across the element 10 will be low enough so that the ignition system may be operated at relatively low electrical voltages. However, the electrical resistivity of the thermal element 10 must be high enough so that the magnitude of the electrical currents which will flow through the thermal element 10 will not be too high to be controlled. The thermal element 10 must be capable of withstanding the violent thermal shock of the extremely rapid heating and cooling cycle to be employed as well as the mechanical vibration and detonation shock waves which normally occur in the combustion chambers of internal combustion 3 engines. Several materials have been used as a thermal element. A variation in electrical resistance of the thermal element 10 of between 0.005 ohm and 0.06 ohm has been satisfactory. The length of the thermal element 10 has varied between 0.02 inch and 0.2 inch and the diameter has varied between 0.004 inch and 0.01 inch. The system has thus far been operated with both conventional low octane gasoline and medium octane gasoline. Such materials as iridium, platinum-clad tungsten, iridium-clad tungsten, and many others can be so used. The material chosen for a particular design problem will depend upon many factors, chiefly the nature of the engine and the fuel used.

Electrical pulses varying in duration between 200 microseconds and one millisecond have been used to provide the necessary heating of the thermal element 10. It should be pointed out that for proper operation it has been necessary, in some engines, that the thermal element 10 be heated to a temperature in excess of 1000 degrees Centigrade. The time necessary to cool the thermal element 10 has not proven critical since for the customary speeds of operation of internal combustion engines, a time in excess of one 100th of a second is available for cooling, and it has been found that the thermal element 10 achieves sufiicient cooling in the order of 5 milliseconds.

The necessary electrical pulses for the actuation of the thermal element originate either from a magneto in engines provided therewith or from circuit breaker points in the case of most battery operated engines. Either the magneto or the breaker points, as the case may be, may provide electrical signals which can be adapted for use as actuating pulses. In general, however, signals originating from the sources described above are not suitable for direct application to the thermal element 10 and are merely used to provide correct timing of the input pulses to the thermal element 10.

FIG. 2 shows a block diagram of electrical and electronic circuitry which is adapted to provide suitable electrical pulses for actuating the thermal element 10 at particular times indicated by the occurrence of pulses from either the magneto or the breaker points. It should be appreciated that, while the particular embodiment shown has been used to actuate the ignition system forming the subject of the present invention, other embodiments or circuits could be designed to operate the system as well. Thus, it is not intended that the present invention should be limited in scope to the circuitry shown and described herein.

In FIG. 2, a pulse source 16 provides electrical pulses which are relatively square in shape and which have a duration which may be controlled, as will be described hereinafter. These pulses commence coincidentally with the arrival of input pulses from either of the sources described above. The pulses appearing at the output of the pulse source 16 are transmitted to the input of a conventional transistor power pulse amplifier 18. The amplified pulses are in turn supplied to the primary winding of an autotransformer 20 which, in eflect, reduces the voltage level of the pulses and increases their current level. The pulses occurring at the secondary winding of the autotransformer 20 have the proper duration and the proper voltage and current levels or magnitudes so that they may be supplied directly to the thermal element 10.

In those situations in which a plurality of thermal elements 10 is used, a distributing device which combines the functions of the autotransformer 20 and a multiple contact switch, will be used instead of the autotransformer 20. As is conventional in internal combustion engines, the distributor is driven from the cam shaft of the engine. The distributing device will be described in detail hereinafter.

FIG. 3 shows the electrical and electronic circuitry comprising the pulse source 16 and the pulse amplifier 18. The pulse source 16 is shown as a monostable multi-vibrator which comprises a pair of PNP transistors 22 and 24 with associated circuitry. The transistor 22 has its base terminal connected to the anode terminal of a diode 26 and to the junction of a pair of resistors 28 and 30. The anode terminal of the diode 26' is connected either to a magneto or to circuit breaker points as described above. The resistor 28 has its opposite end connected to a bias voltage supply which may be of the order of minus 6 volts D.C. The resistor 28 may have a value of approximately 30,000 ohms and the resistor 30 may have a value of approximately 4,700 ohms. The collector terminal of the transistor 22 is connected to the D.C. supply voltage which may be approximately minus 10 volts through a resistor 32. The emitter terminal of the transistor 22 is connected to common or ground potential. The collector terminal of the transistor 22 is further connected to the base terminal of the transistor 24 through a capacitor 34 which may be of the order of 0.15 microfarad.

The opposite end of the resistor 30 is connected to the collector terminal of the transistor 24. The collector terminal of the transistor 24 is also connected to the junction of a pair of resistors 36 and 38 which may have values of and 560 ohms respectively. The opposite end of the resistor 36 is connected to the minus 10 volt D.C. supply. The emitter terminal of the transistor 24 is connected to common or ground potential and the base terminal is further connected to the minus 10 volt D.C. supply through a resistor 40, which may have a value of 4,700 ohms. A capacitor 42 which may have a value of 50 microfarads, is connected between the minus 10 volt D.C. supply and common or ground potenital.

The opposite end of the resistor 38 is connected to the base terminal of a PNP transistor 44 through a capacitor 46 which may have a value of 50 microfarads. The base terminal of the transistor 44 is also connected to common or ground potential through a resistor 48 which may have a value of 500 ohms. The emitter terminal of the transistor 44 is connected directly to ground and the collector terminal is connected to the minus 10 volt D.C. supply through a parallel combination comprising a diode 50, having its anode connected to the minus 10 volt D.C. supply and its cathode connected to the collector terminal of the transistor 44, and the total resistance of a potentiometer 52. This resistance may be of the order of 25 ohms.

A pulse transformer 54 has one end of its primary winding connected ot the minus 10 volt D.C. supply and the opposite end of the primary winding connected to the variable tap of the potentiometer 52. The secondary winding of the pulse transformer 54 has one end connected to common or ground potential and the opposite end connected to the base terminals of a pair of PNP transistors 56 and 58. The emitter terminals of the transis tors 56 and 58 are connected together and to common or ground potential. The collector terminals of the transistors 56 and 58 are also connected together and to one end of the total winding of an autotransformer 60. The opposite end of the winding of the autotransformer 60 is connected to the minus 10 volt D.C. supply voltage. A diode 62 isconuected across the total winding of the autotransformer 60, having its cathode connected to the junction of the collector terminals of the transistors 56 and 58 and its anode connected to the minus 10 Value D.C. supply. The output of the autotransformer 69 is obtained between the minus 10 volt D.C. supply and the intermediate tap of the autotransformer 60.

The transistor 22 and 24 and the circuitry associated therewith, form a circuit known as a monostable multivibrator. Such a circuit assumes a stable configuration or state until triggered by an input pulse, whereupon the circuit switches to an unstable state, and remains thus for a predetermined time before returning to the original stable state. The circuit is similar to the well known bi-stable m-ulti-vibrator or flip flop except that one crosscoupling network permits A.C. coupling only. Therefore, the circuit can only remain in its unstable state until the reactive component (capacitor 34) dis-charges.

With the -PNP transistors used, a trigger pulse must be a negative going pulse which is applied to the base of the transistor 22 through a diode 26. The diode 26 is necessary since the Waveform of the input pulses from the magneto or breaker points includes unwanted positive portions. The base of the transistor 22 is coupled to the collector of the transistor '24 through a D.C. coupling, the resistor 30. The base of the transistor 24 is coupled to the collector of the transistor 22 through an A.C. coupling, the capacitor 34. The resistors 32 and 36 serve as load resistors for the transistors 22 and 24 respectively. The resistor 40 adjusts the bias on the base of the transistor 24, and the resistor 28 adjusts the bias on the base of the transistor 22. The capacitor 42 serves as an A.C. filter for the minus volt D.C. supply.

The duration of the output pulse, that is the length of time the circuit remains in its unstable state, is controlled by a RC network comprising the input imipedence to the transistor 22, the resistor 28 and the resistor '32 along with the capacitor 34. In effect, the size of the capacitor 34 is the controlling factor in determining the duration of the output pulse. The output of the monostable multivibrator is coupled to a conventional amplifier stage through a current limiting resistor '38 and a coupling capacitor 46, which are connected in series to the base of the transistor 44. The potentiometer '52 serves as the load resistor and the resistor 48 .as the bias resistor for the transistor 44. The potentiometer 52 also serves to adjust the output of the device. The diode 50 serves to protect the transistor 44 from voltage kick-backs due to the transformer '54.

The output of the amplifier stage is coupled through the transformer 54 to a pair of power amplifying transistors 56 and 58, in parallel. This amplification stage is also conventional. The load element is the winding of the autotransformer 60 which also functions to decrease the voltage of the output pulse and increase the current of the pulse. The diode 62 protects the transistors 56 and 58 from kick-backs due to the action of the autotransformer 60. 1

Turning now to FIG. 4, there is shown the details of construction of a distributor or switching element operating on a variable reluctance principle. A rotatable shaft 64 has a movable cylindrical body 66, rotatable with said shaft 64 and composed of magnetizable material having a relatively low magnetic reluctance, mounted on and concentric with the shaft 64. The cylindrical body 66 is furnished with a projecting lug or tab 68 which forms an integral portion of the cylindrical body 66. A fixed element 70, composed of magnetizable materiahencloses the cylindrical body 66. The fixed element 70 is cylindrical in shape and has an end portion which extends toward the cylindrical body "66 such that the end portion lies adjacent the body '66. There is, however, enough clearance between the end portion and the body 66 such that the cylindrical body '66 is free to rotate.

A plurality of extending arm portions 71 composed of magnetizable material are affixed to the fixed element 70 forming butt joints therewith such that the joints add relatively little effective air gap to the magnetic path through the fixed element 70. In general, the arm portions 71 will be substantially equally spaced around the inner circumference of the fixed element 70 and lie in the plane formed by the rotation of the projecting lug 68. The lengths of the arm portions 71 are fixed such that the projecting lug 68, when it is in particular orientations, lies immediately adjacent the arm portions 71. As may be seen in FIG. 4, rotation of the shaft 64 produces successive magnetic coupling between each arm portion 71 and the cylindrical body 66, as the projecting lug 68 successively lies adjacent each of the arm portions 71.

A primary winding 72 is inserted within the fixed element 70 and remains fixed with respect to the rotating shaft 64 and the cylindrical body 66. Each of the arm portions 71 is provided with a secondary winding. FIG. 4 shows a fixed element 70 comprising two arm portions, said arm portions having secondary windings 74 and 76 mounted thereon. The primary winding 72 is adapted to receive pulses from the collector terminals of the transistors 56 and 58, as shown in FIG. 3. As each such pulse is received, it may only be transmitted to that secondary winding mounted on the arm portion 71 adjacent the projecting lug 68. The shaft 64 is rotated such that when the next pulse is received by the primary winding 72, the projecting lug 68 will be adjacent another arm portion 71 and another secondary winding will be actuated. It is evident that only that secondary winding can be actuated, the arm portion of which lies adjacent the projecting lug 68, since the magnetic path through the projecting lug 68 is the only magnetic path which inheres a low enough magnetic reluctance that effective magnetic coupling may result.

While FIG. 4 only shows a pair of secondary windings, it is evident that the magnetic distributor may be used with as many secondary windings as may be desired.

Each secondary winding is connected to a thermal element through a pair of wires 78, and the primary winding 72 is connected to the source of input pulses through a pair of wires 80. 6

Thus the magnetic distributor provides successive con nection to a plurality of thermal elements without any actual electrical contact. In addition, the ratio of the number of turns on the primary winding to the number of each secondary winding is made relatively large so that the voltage of the electrical pulse supplied to the primary winding is decreased and the current increased.

It may now be appreciated that a novel and improved ignition system has been described, which achieves those objects and advantages enumerated above as well as others which are now apparent. In addition, a novel magnetic distributor has been described. Such a distributor is particularly adapted for use in the ignition system forming the present invention. However, the distributor is adapted to beused in other configurations and for other purposesthan those mentioned herein.

It is also apparent that other embodiments of the present invention, differing only in detail therefrom, could be described. It is also not intended that the breadth of the appended claims should be limited to those details herein described.

What is claimed is;

r 1. An ignition system for an internal combustion engine having a combustion chamber for receiving an airfuel mixture comprising: a low resistivity thermal element for igniting the air-fuel mixture, said element mounted in the combustion chamber, and adapted to receive electric currents in excess of one hundred amperes for less than one millisecond and to respond immediately thereto by changing temperature in accordance with said currents; and electric current providing means electrically coupled .to said thermal element for providing electrical pulses of less than one millisecond duration at low volttages of the order of ten volts and high currents in excess of amperes.

2. An ignition system for a multi-cylinder internal combustion engine in which each cylinder has a combustion chamber for receiving an air-fuel mixture comprising: a

plurality of thermal elements for igniting the air-fuel mixproviding electrical pulses of relatively short duration at low voltage and high current; and a magnetically operated electrical distributor for successively connecting said electric current providing means to each of said plurality of thermal elements, said distributor comprising a rotatable shaft, a movable body mounted on, and concentric with, said shaft and rotatable therewith, said body being composed of magnetizable material having a relatively low magnetic reluctance, said body including a projecting lug extending outwardly from said body at one point on the circumference of said body, a fixed element composed of magnetizable material having a relatively low magnetic reluctance enclosing said movable body, said fixed element including a plurality of arm portions extending inwardly toward said movable body in the plane formed by the rotation of said projecting lug such that rotation of said shaft moves said projecting lug to positions successively adjacent each of said arm portions, a primary winding electrically connected to said electric current providing means and mounted within said fixed element, said primary winding enclosing said movable body and magnetically coupled thereto, and a plurality of secondary windings, each of said plurality mounted on one of said arm portions, enclosing said arm portion and magnetically coupled thereto, each of said plurality being electrically connected to one of said plurality of thermal elements.

3. An ignition system for a multi-cylinder internal combustion engine in which each cylinder has a combustion chamber for receiving an air-fuel mixture comprising: a plurality of thermal elements for igniting the air-fuel mixture within the combustion chambers, said plurality being distributed such that at least one of said elements is mounted in each of the combustion chambers, each element being adapted to receive electric currents and to respond thereto by changing temperature in accordance with said currents; timing means for providing electrical signals at particular times; electrical signal providing means electrically coupled to said timing means and to each of said thermal elements for providing electrical pulses of relatively short duration at low voltage and high current at said particular times; and a magnetically operated electrical distributor for successively connecting said electrical signals providing means to each of said plurality of thermal elements, said distributor comprising a rotatable shaft, a movable body mounted on, and concentric with, said shaft and rotatable therewith, said body being composed of magnetizable material having a relatively low magnetic reluctance, said body including a projecting lug extending outwardly from said body at one point on the circumference of said body, a fixed element composed of magnetizable material having a relatively low magnetic reluctance enclosing said movable body, said fixed element including a plurality of arm portions extending inwardly toward said movable body in the plane formed by the rotation of said projecting lug'such that rotation of said shaft moves said projecting ulg to positions successively adjacent each of said arm portions, a primary winding electrically connected to said electrical signal providing means and mounted with said fixed element, said primary winding enclosing said movable body and magnetically coupled thereto, and a plurality of secondary windings, each of said plurality mounted on one of said arm portions enclosing said arm portion and magnetically coupled thereto, each of said plurality being electrically connected to one of said plurality of thermal elements.

4. A device according to claim 2 in which said pri mary winding has a greater number of turns than said secondary windings.

5. A device according to claim 3 in which said primary winding has a greater number of turns than said secondary windings.

6. An electrical switch having an input and a plurality .of outputs, said switch comprising: a rotatable shaft, a

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movable body mounted on, and concentric with said shaft and rotatable therewith, said body being composed of magnetizable material having a relatively low magnetic reluctance, said body including a projecting lug extending outwardly from said body at one point on the circumference of said body; a fixed element composed of magnetizable material having a relatively low magnetic reluctance enclosing said movable body, said fixed element including a plurality of arm portions extending inwardly toward said movable body in the plane formed by the rotation of said projecting lug such that rotation of said shaft causes said projecting lug to lie adjacent each of said arm portions successively; a primary winding electrically connected to said input element and mounted within said fixed element, said primary winding enclosing said movable body and magnetically coupled thereto; and a plurality of secondary windings, each of said plurality mounted on one of said arm portions, enclosing said arm portions and magnetically coupled thereto, each of said plurality being electrically connected to one of said plurality of output elements.

7. A device according to claim 6 in which said primary winding has a greater number of turns than said secondary windings.

8. A magnetically operated electrical distributor for successively connecting a source of electric current to each of a plurality of ignition elements, said distributor comprising: a rotatable shaft, a movable body mounted on, and concentric with, said shaft and rotatable therewith, said body being composed of magnetizable material having a relatively low magnetic reluctance, said body including a projecting lug extending outwardly from said body at one point on the circumference of said body, a fixed element 'composed of magnetizable material having a relatively low magnetic reluctance enclosing said movable body, said fixed element including a plurality of arm portions extending inwardly toward said movable body in the plane formed by the rotation of said projecting lug such that rotation of said shaft moves said projecting lug to positions successively adjacent each of said arm portions; a primary winding electrically connected to said source of electric current and mounted within said fixed element, said primary winding enclosing said movable body and magnetically coupled thereto, and a plurality of secondary windings, each of said plurality mounted on one of said arm portions, enclosing said arm portion and magnetically coupled thereto, each of said plurality being electrically connected to one of said plurality of ignition elements.

9. A device according to claim 8, in which said primary winding has'a greater number of turns than said secondary windings.

10. An ignition system for a multi-cylinder internal combustion engine in which each cylinder has a combustion chamber for receiving an air-fuel mixture comprising: a plurality of thermal elements for igniting the airfuel mixture within the combustion chambers, said plurality being distributed such that at least one of said elements is mounted in each of the combustion chambers, each element being adapted to receive electric currents and to respond thereto by changing temperature in accordance with said currents; electric current providing means electrically coupled to each of said thermal elements for providing electrical pulses of relatively short duration at low voltage and high current; and a magnetically operated electrical distributor for successively connecting said electric current providing means to each of said plurality of thermal elements, said distributor comprising a rotatable shaft, a movable body mounted on, and concentric with, said shaft and rotatable therewith, said body being composed of magnetizable material having a relatively low magnetic reluctance, said body including an extending portion which extends from one point on the circumference of said body, a fixed element composed of magnetizable material having a relatively low magnetic reluctance enclosing said movable body, said fixed element including a plurality of arm portions extending toward said movable body in the plane formed by the rotation of said extending portion such that rotation of said shaft moves said extending portion to positions successively adjacent each of said arm portions, a primary Winding electrically connected to said electric current providing means and mounted within said fixed element, said primary Winding enclosing said movable body and magnetically coupled thereto, and a plurality of secondary windings, each of said plurality mounted on one of said arm portions, enclosing said arm portion and magnetically coupled thereto, each of said plurality being electrically connected to one of said plurality of thermal elements.

11. An electrical switch having an input and a plurality of outputs, said switch comprising: a rotatable shaft; a movable body mounted on, and concentric with said shaft and rotatable therewith, said body being composed of magnetizable material having a relatively low magnetic reluctance, said body including an extending portion which extends from one point on the circumference of said body; a fixed element composed of magnetizable material having a relatively low magnetic reluctance enclosing said movable body, said fixed element including a plurality of arm portions extending toward said movable body in the plane formed by the rotation of said extending portion such that rotation of said shaft moves said extending portion to positions successively adjacent each of said arm portions; a primary winding electrically connected to said input element and mounted within said fixed element, said primary winding enclosing said movable body and magnetically coupled thereto; and a plurality of secondary windings, each of said plurality mounted on one of said arm portions, enclosing said arm portions and magnetically coupled thereto, each of said plurality being electrically connected to one of said plurality of output elements.

12. A magnetically operated electrical distributor for successively connecting a source of electric current to each of a plurality of ignition elements, said distributor comprising: a rotatable shaft; a movable body mounted on, and concentric with, said shaft and-rotatable therewith, said body being composed of magnetizable material having a relatively low magnetic reluctance, said body including an extending portion which extends from one point on the circumference of said body; a fixed element composed of magnetizable material having a relatively low magnetic reluctance enclosing said movable body, said fixed element including a plurality of arm portions exextending toward said movable body in the plane formed by the rotation of said extending portion such that rotation of said shaft moves said extending portion to positions successively adjacent each of said arm portions; a primary winding electrically connected to said source of electric current and mounted Within said fixed element, said primary winding enclosing said movable body and magnetically coupled thereto, and a plurality of secondary windings, each of said plurality mounted on one of said arm portions, enclosing said arm portion and magnetically coupled thereto, each of said plurality being electrically connected to one of said plurality of ignition elements.

References Cited by the Examiner UNITED STATES PATENTS 1,823,217 9/31 Sparkes 31783 2,403,290 7/46 Korman 123145 2,484,544 10/49 Bennett et al. 2l9270 2,584,907 2/52 Nelson 200-19 2,933,896 4/60 Ferric 3l7-83 X RICHARD M. WOOD, Primary Examiner. 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE HAVING A COMBUSTION CHAMBER FOR RECEIVING AN AIRFUEL MIXTURE COMPRISING: A LOW RESISTIVITY THERMAL ELEMENT FOR IGNITING THE AIR-FUEL MIXTURE, SAID ELEMENT MOUNTED IN THE COMBUSTION CHAMBER, AND ADAPTED TO RECEIVE ELECTRIC CURRENTS IN EXCESS OF ONE HUNDRED AMPERES FOR LESS THAN ONE MILLISECOND AND TO RESPOND IMMEDIATELY THERETO BY CHANGING TEMPERATURE IN ACCORDANCE WITH SAID CURRENTS; AND ELECTRIC CURRENT PROVIDING MEANS ELECTRICALLY COUPLED TO SAID THERMAL ELEMENT FOR PROVIDING ELECTRICAL PULSES OF LESS THAN ONE MILLISECOND DURATION AT LOW VOLTTAGES OF THE ORDER OF TEN VOLTS AND HIGH CURRENTS IN EXCESS OF 100 AMPERES. 